. >>> the pentagon made a big announcement as we headed into the weekend. it's putting the country's single largest weapons program on hold. all 51 of the pentagon's new f-35 fighter jets will be grounded following the discovery of a cracked turbine blade in one of the plane's engines. it's the second time in two weeks the government has had to pause the $396 billion weapons program. >>> trouble for another big program tonight. at this moment the most contaminated nuclear site in the country is leaking a mix of radioactive and toxic material into the soil. the waste is coming from old underground tanks in washington state's hanford nuclear reservation, a site that produced plutonium for the bombs dropped in world war ii. officials say the leak is not an immediate threat since it will likely take years for the chemicals to reach the groundwater. >>> when "nightly news" continues on this saturday, finding the next big breakthroughs in medicine. a new generation of scientists gets millions to make it happen. >>> the new power of the internet is driving a song